1. Institute of New Energy Material Chemistry, Institute of Scientific Computing, Nankai University, Tianjin 300071, P. R. China, State Key Laboratory of Materials Modification by Laser, Electron, and Ion Beams and College of Advanced Science and Technology, Dalian University of Technology, Dalian 116024, P. R. China, and Department of Chemistry and Center for Computational Chemistry, University of Georgia, Athens, Georgia 30602